If you’ve already heard that dinosaurs are extinct — and the betting is that you have — you’ve probably also heard the reason: an asteroid smashed into Mexico’s Yucatán Peninsula some 65 million years ago, blasting enough dust into the atmosphere to block the sunlight and dim the skies. These days that’s Intro to Dinos stuff, but prior to 1980, the thinking was very different. Dinosaurs endured a long, slow decline, the theory went, ceding their rule of the planet only gradually and grudgingly. The old theory is nearly as extinct as the beasts themselves — or at least it was until last week, when a new study pumped a little life back into it. About 200,000 years before the asteroid hit, a separate extinction was already under way, wiping out numerous species of clams and snails on the ocean floor. And it was terrestrial volcanoes, not a rock from space, that were to blame.

The new findings, published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology, are the product of three years of summer visits by researchers to Seymour Island, on the Antarctic Peninsula. Polar regions make research hard — one year the ice was so thick that the scientists’ boat couldn’t reach the shore — but when the weather cooperates, the sites offer fossil hunters distinct advantages. One is that, like today, the ancient poles were more susceptible to climate change. Ice then was the same as ice now, which is highly reflective. As it melts, it gives way to darker ocean water, which absorbs more light and heat, exacerbating warming in an accelerating loop. In this case, scientists wanted to determine temperatures in the polar ocean from 65 million years ago, so they gathered more than 100 ancient, 2-in.-wide (5 cm) shells from subterranean samples, then analyzed the minerals and calcium carbonate that had formed the shells.

Those ancient artifacts revealed a lot. Calcium carbonate — an organic stew of calcium, carbon and oxygen — is nature’s answer to a stuck thermostat, with the environmental conditions when the material formed forever stamped into its chemical makeup. The oxygen portion has two variants: oxygen-16 and oxygen-18. If there’s more oxygen-16, seawater temperatures were higher when the shell formed — and that’s exactly what the scientists discovered, in this case an estimated 9ºF (5ºC) temperature jump from typical seawater temperatures. By matching that information with the strata layers where those oxygen-16-rich shells were found, geologists identified three periods of ocean warming: about 2 million years before the great dinosaur extinction, then 250,000 years before and again about 200,000 years after.

All three of those eras coincide nicely with volcanic events in India’s Deccan Plateau, which may have belched enough carbon dioxide and other greenhouse gases to boost planetary temperatures and harm ocean dwellers. “If this warming is severe enough to be impacting marine life, it’s likely impacting terrestrial life too,” says Tom Tobin, a doctoral student at the University of Washington and the report’s lead author. “So it’s not unreasonable to think that the environmental stress from the volcanism contributed to the strength of the asteroid extinction. One of [the events] is synchronous with the marine extinction that we found 200,000 years before the asteroid impact.”

Such relatively specific dates underscore another reason the scientists chose their Antarctic research site: it offers unusually thick, 3,200-ft.-deep (1,000 m) sediment, and the deeper the sediment is, the more layers of geologic time have been preserved. This region apparently built up more than most because of repeated sediment deposits during uplift of the mountain range that makes up the Antarctic Peninsula. In fact, the Seymour Island site has so many sediment layers that scientists could whittle the time intervals down to hundred-thousand-year scales — a minuscule window compared with the 10-million-year degree of accuracy most sites provide.

Even this geologic precision, however, wasn’t enough to seal the deal, at least not to an acceptable scientific certainty. So the scientists used an imaginative method, matching changes in Earth’s magnetic field to different layers in the strata. Though most people assume magnetic north is a constant, it isn’t. Every 500,000 years or so — and in random periods ranging from as little as 100,000 years to 30 million years — the magnetic north pole flips to the south pole. When it does, magnetic particles in slow-building sediments orient themselves accordingly, then become locked in place as further sediment builds.

With this in mind, the researchers drilled core samples and compared the particles’ orientation with the known history of magnetic-field changes. That provided confirmation that the earlier oceanic extinctions occurred within the range of Deccan volcanism. “Once we compared the warming record to the timing of the volcanism,” says Tobin, “we realized, Hey, these things seem to line up pretty well. This is pretty cool. It brings more complexity and nuance to the picture we already had.”

Intrigued by the possibility of further reconciling extinction theories, the researchers are searching for a second site with the rare, deep sediment layers necessary for a close-up look at the late-Cretaceous period. For the moment, it seems that both volcanoes and the infamous asteroid may have contributed to the dinosaurs’ demise — a tidy addendum to Dino 101.

It's a pretty believable scenario, but being able to define a separation of 200,000 years is a very, very difficult undertaking. I'm not sure that radiometric dating has error bars significantly less than that, which certainly means the Chixulub impactor's timing can't be constrained more tightly.

There are two problems I see:

1. The 5C increase is not particularly significant as an impact on life, secular warming (still caused by the Deccan Taps) features much greater polar temps, and may have even enhanced life for dinosaurs in polar regions - without significantly impacting equatorial zones. Any dieoffs recorded locally in the sea may be attributed to changes in polar temperatures only, and not even across the planet, let alone all the oceans. We see this in Quaternary sediments with a vengeance.

2. Though geological superposition rules apply to the strata that were studied, it is extremely difficult to prove that, given the error bars in dating the iridium / impact layer, that sedimentary deposition took place at the same rate throughout the geological column.

Like I said, believable, but there are too many ifs. They have to prove that life on both land and sea worldwide was affected from the equator to the poles for this one to stick!

My favorite quote...from "The Life of PI",..."Agnostics.... are under the thrall of reason, that fool's gold for the bright....Atheists are my brothers and sisters of a different faith....Like me they go as far as the legs of reason will carry them----and then they leap."

I guess this is the dinosaur second gunman on the grassy knoll theory. Seriously, good article, although if anyone has watched some of the finer scientific documentaries dealing with all of this over the last few years, it is often clearly stated that before the asteroid impact, the dinosaurs were already under extreme stress and being thinned out by rapid climate changes, which partly involved lots of volcanic eruptions and greatly reduced food supplies. Of course birds are now said to be the only survivors of the dinosaur line.

Somehow it makes the dinosaur story even sadder that their remaining toughest surviving members, after having soldiered through countless natural disasters, from reversing magnetic poles, to mega-volcanoes, find themselves looking up into the sky only to see a humongous space rock heading straight for them. "What are the chances?" you can almost imagine them remarking. We've all had days like that.

Of course we are currently living through another historic period of massive extinctions, this one caused by humans, mostly through habitat destruction. So we can think of ourselves as being the modern day equivalent of a brainless unbelievably destructive big fat asteroid.

The idea that dinosaurs were dying off well before the impact were put forward by Bakker in the mid '80s and supported by many until the the Signor-Lipps effect was recognized as a potential spoiler i.e. rare fossils are harder to find than common fossils. UW prof Peter Ward did ammonite counts in the '80s and '90s, first supporting, then later finding their remains within 10 cm of the impact layer, too.

Since then, studies showed that there are dinosaur remains up to within the last few cm of the impact layer. Also, there is the question of dating errors, sediment rates, etc that I outline below.

Readers should keep in mind the power of the paradigm to profoundly affect the interpretation of past data. All of this data mentioned fits very well within a recent flood scenario, even better actually. It's very strange that the past is so littered with these random massive extinctions that completely decimate the most unexpected species, while leaving other, more vulnerable ones, intact and unchanged up to today. If we see the fossil record as the record of successive destruction of a flood however, the data begins to make much more sense. All this scientifique study proves is that the burial of this sea life was happening at the same time as those volcanos were errupting. But it could have very well happened within a very short time, during a global tectonic catastrophe that recycled the ocean floor and flooded all the continents, as UCLA and Los Alamos national laboratories geophysicist John Baumgardner proposed and modelled in Tera, a real-time tectonic simulation program. I also found amusing the suggestion that dating layers using the magnetic orientation of volcanic rocks in those layers somehow novel or groundbreaking. This method has been around for almost 40 years.

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Arg. This here paleontology is a mighty shifting sort. One days she's a blaming an asteroid, the next she's a blaming the volcanoes too. For goodness sake's do we have to blame the poor misunderstood asteroid just doing it's job floating 'round the solar system.? Aye, but oooooohhhh that's not enough now we must also attack a hard working volcano. Just puttin'in his geologic nine to five and lo 65 million years later he's a gettin' the blame for killin' the precious dinos. For the love of Pete can't a mere celestial phenomenon and a domestic geologic disturbance get a break around here.

So, after the big rock hit our planet and the poles reversed and all the Dino's died (except those that were smart enough to evolve wings and learend to fly?), where did Homosapians come from? Did we just grow out of the organisms left in the muck? Or did the much grow apes that evolved into Homosapians? (spelling??). Oh wait, there were 3 disctinct versions of man.......... interesting...... SO only some of the apes evolved and the rest decided to stay apes? What has evolved lately, or did evolution just stop now that we exits???????????? Ok.... you are right! The Earth and all that lives on it are the result of some great cosmic accident. SOme rocks crashed into each other and Coalesced created a perfect environment for life........ awesome........... For all atheists, who has more to lose by being wrong?

What's of interest is the carbon in the calcium carbonate. C12/C13 ratios tell whether the carbon came from volcanos (C13 heavy by +5 per mil PDB), or from living creatures (C13 light by -25 per mil PDB or more).

Detecting this kind of carbon fractionation is pretty old science, now, curves have been traced back almost 3.8 billion years.

BLASPHEMY! How could the dinosaurs die out 65 million years ago if the Earth was only created only a few thousand years ago? Everyone knows that people were riding dinosaurs (ala the Flintstones) and they all died out as a result of Noah's flood.

I consulted Faux News and as I expected extinction was actually Obama's fault. Murdoch was actually there at the extinction and just like his news, their version is much more entertaining than the facts.

not only was a nurse discussing the trust issues of looking at hemoglobin under a microscope, but the dinosaur specialsists that confirm that the Reptilian stegosaurus has a brain the size of a walnut is convincing too.

So theists proof for god is that if scientists can't explain it then god must of did it? So a discussion 200 yrs ago where physicists could not explain why planets retrograde would been an argument for theists that god exists. Problem is for theists is physicists do know why planets retrograde. If that is how theists want to invoke their proof for god, then god is a ever receding pocket of scientific ignorance that is getting smaller and smaller. The god of the gaps if you will.

"Junk. Barren. Non-functioning. Dark matter. That’s how scientists had described the 98% of human genome that lies between our 21,000 genes, ever since our DNA was first sequenced about a decade ago. The disappointment in those descriptors was intentional and palpable."

You believers are so pathetic and evil if you really think some god will sentence non-believers to eternal damnation just for not believing in something there is no proof for what so ever...

Even worse, you truly believe a rapist and a murderer who suddenly "finds god" will be spared, and some atheist who never hurt anyone and was a good parent will end up in hell... You not only agree with that "punishment" but gloat over it while you offer your "divine insight".

How evil is that, and why would anyone want to believe in and submit to such an evil deity and practice such an evil religion?

god is god. no one can prove if he?/she /It/higher power/nature( "is or isn't).we will find out when we die.some sooner,some later.one thing for sur e,if our planet was 50000 miles closer to the sun OR 50000 miles farther from the sun their would be no life on this planet

The trouble for believers in invisible sky friends is that they have no proof of their beliefs. Only "faith", which is to say an unquestioning belief that what they're told by a Bronze Age myth and which is perpetuated by mortal men whose secular power and wealth is enhanced by doing so is true.

Nature says otherwise.

In fact, there's no room in physics (or nature if you will) for invisible sky friends. No need. No reason. No place. All one has to do is merely say that we are human and aren't born with all the answers - an inherently logical and rational thing to assume. But given human curiosity and the ability to explore our existence, answers are not beyond our understanding.

To assume otherwise is irrational. To say that because we don't YET understand all of it, then it must be the domain of an invisible sky friend is - from a psychological point of view - not only irrational, but delusional as well.

All REAL evidence suggests that once death occurs, consciousness ceases. People have a hard time dealing with this concept. It makes the smug, self-righteous and delusional among us believe that those they disagree with are being punished and those who they agree with are being rewarded when the overwhelming likelihood is that they are simply no more, care not and know nothing at all.

There is no objective evidence that miracles exist or defy eventual understanding. When the believers call it "god's work", they stop thinking of all the possible reasons that it actually happened and cut off all thought of exploring those reasons so that these alleges "miracles" can become an every day occurrence for those who need them due to scientific exploration and discovery.

Further, the divisions caused by organized religion and the "faithful" in society and the world are the root cause of untold violence and suffering - far in excess of the alleged "good" they do. More often religious leaders live in luxury on the donations of those who live in squalor who try to "buy" their way into heaven while adhering to tenants that they expect others to follow but find it impossible to follow themselves.

The bottom line is that those who believe in irrational things are those who are irrational. Trying to force their irrationality on the rest of us is not only delusional, but detrimental to the survival of the human species. Religion will kill us all. The truly sad part of that is that those faithful who die and end up merely compost in the ground whose existence as a conscious entity has ended won't be suffering the wrath of their childish sky friend for destroying his alleged creations. Like the rest of us, they'll simply cease to exist.

Imagine a world where every human life was as brief as it actually is - no souls. No heaven. No hell. Nothing after death at all. If people lived knowing these things, one would think they'd act a hell of a lot differently than the believers do today.

No one WANTS you to go to hell. God wants EVERYONE to be in heaven. He wouldn't have sacrificed a son He loved if He didn't.

My thoughts on this, for what they are worth - heaven and hell are not physical places so much as spiritual conditions. Even after your physical body dies, your spirit lives on. Hell is the absence of God, or a separation from God. Heaven is to be in a relationship with God. You choose to be in that relationship with God or not. It's your choice. You can't blame God for your own choices. He gave you freedom to choose - He did not create you as an automaton, but as an individual with free will. However, because you have free will, you are responsible for the consequences of your own choices.

If you don't believe in heaven or hell, though, then none of this is relevant to you - so why do you even care?

BTW, I believe in both God and evolution. I don't see a contradiction. the passage in the Bible where it talks about Creation uses the word "day", but the actual word in the original text can be interpreted to mean "period of time" where the time period is of indeterminate length. So there is no Biblical reason not to believe in a billions-year old Universe.

@JasonFontaine:disqus Unlike most of your fellow believers, I never experienced any desire to wish for anything bad to happen to any believer (or anyone else having a different opinion on any issue) no matter what my opinion on his or hers beliefs is. To wish for bad things for someone you don't agree with is quite simply a psycho-pathological problem. That is why I find it mind-boggling when I see how many believers gloat over what they think is a fact that non-believers will burn in hell for their lack of belief.

If you had fully developed your critical thinking abilities when you read the bible the first time and concluded that it was the true word of god and the word you shall follow all your life, all the power to you, I have no problem with you as long as you don't wish me and my family burn in hell for not having the same beliefs.

If, on the other hand, you were scared into faith with stories about hell and damnation at a very young age (like most children were) and now you're doing the exact same thing to your children, your actions, in my opinion, amount to nothing short of child abuse... But still, I wish you no harm, I just wish there was a way to ensure no child would be introduced to such amazing ideas, not based in reality, before their critical thinking skills were fully developed, even if it had to be regulated by the laws...

It is the greatest sin - to deny Him. I pray you will find peace - and if peace is through atheism - more power to you - I simply have faith - and that's all it is....much of your statement is correct - just skewed a little~ :) Blessings to you and yours